The dangers of tsunamis are generally well known and, at least since December 2004 when a tsunami devastated wide areas bordering the Indian Ocean, much publicised. Early warning systems, intended to provide warning messages before the arrival of a tsunami have been proposed. Such warning messages are e.g. issued after the occurrence of an underwater earthquake, which may be considered the most common trigger of a tsunami.
In order to prevent loss of life, it is important to provide tsunami warnings to potentially affected areas quickly so that these areas can be evacuated.
WO 2006/079513 discloses a tsunami alarm system wherein information on the possibility of a tsunami occurring is collected on the Internet. The system monitors the Internet to seek information about the likely occurrence of a tsunami. If such a warning is detected, a warning consolidation procedure is triggered. The consolidation may include a pre-alarm to a supervisor of the alarm system and the attempt to verify the original message. Alternatively, the consolidation may include an automatic assessment procedure consisting of the attempt to verify the original message without supervisor intervention. Once the warning is verified, either manually or automatically, an alarm is raised and a distribution list manager sends an alarm message via a mobile telephony network to all subscribers of the alarm list. The alarm message may also comprise further information, such as a description of the region of the tsunami hazard.
A drawback of this system is that the mobile phone user must have subscribed to the service and must have their mobile phone on them in order to receive the tsunami alarm message. However, many beachgoers, often foreign tourists, do not carry their mobile phone when on the beach or have not subscribed to such a service. It follows that the tsunami warning message may not reach the people most at risk. In addition the system does not take into account the location where the phone user is and alerts all subscribers independently on their current location.